1. Field of the Invention
This invention relates generally to an automatic head scan tracking system and is directed more particularly to an automatic head scanning system for improving signal reproduction at tape speeds which are different from the tape speed during signal recording.
2. Description of the Prior Art
In the use of video tape recorders, the situation often occurs where the magnetic tape speed during reproduction of a recorded signal is different from the speed that the signal was recorded at such as to achieve slow motion, still motion or quick motion picture reproduction. In order to carry out such reproduction at the different tape speeds and maintain picture quality, there has been proposed an automatic head scan tracking system having by a deflection device or deflector formed by an electro-mechanical transducer for performing a servo function to make the reproducing head accurately scan the recording track.
It is, known however that the deflector used in the above prior art system suffers from two defects. One defect is a transient vibration caused in the deflector when the deflector begins to move, which transient vibration deteriorates the reproduced picture. This first defect can be aboided some what by damping the deflector mechanically but it is difficult to eliminate the defect entirely. Also there is a possibility that the damping effect may be reduced by secular variation with the passage of time. The other defect, though depending upon the kind of deflector, is a hysteresis effect necessitating a closed loop servo in the tracking system with the result that the system becomes more complicated.